Circular tuning fork timepiece



NOV 9, 1965 MAsAKAZU HlRosE ETAL 3,215,188

CIRCULAR TUNING FORK TIMEPIECE 2 Sheets-Sheet l Filed June l2, 1964 l NOV- 9, 1965 MAsAKAzU HlRosE ETAL 3,216,138

CIRCULAR TUNING FORK vTIMEIPIECE Filed June l2. 1964 2 Sheets-Sheet 2 Hg 4 F/g 5 United States Patent O 3,216,188 CIRCULAR TUNING FORK TIMEPIECE Masakazu Hirose and Koichi Iwaki, Gyoda, Japan, as-

siguors to Jeco Company,Lmited, Tokyo, Japan, a

corporation of Japan Filed June 12, 1964, Ser. No. 374,580

Claims priority, application Japan, `luly 14, 1963, 38/

38,338, 13S/38,339; Dec. 5, 1963 (utility model), 38/

4 Claims. (Cl. S8-23) This invention relates to timepieces comprising circular tuning forks.

In the conventional timepiece, time is kept by the reciprocating motion of a balance wheel which is oscillated by mechanically accelerating the force of a mainspring through gear trains and a mechanical escapement or reciprocated by an electric energy by means of a coil or magnetic element and an electric contact attached to a balance wheel, converti-ng the reciprocating motion to a rotary motion.

As the balance wheel is used as a mechanical oscilllator therein, the quality yfactor Q of the balance wheel itself will be so low that no highly accurate timepiece will be obtained.

A pendulum is a little higher in the quality factor Q than the balance wheel but is so troublesome in arranging the hanging post-ure of the pendulum clocks that it cannot be applied to watches.

Further, in more highly accurate timepieces, time is indicated by the means mechanically converting the oscillating motion of a tuning fork to a rotary motion by a ratchet mechanism. However, it has such complicated mechanism in converting the oscillation of the tuning fork to a rotary motion that the working yield is low, the product is lcostly and the converting method is not adapted to mass-production and is not general. The present invention has been suggested to eliminate the above mentioned defects.

A principal object of the present Iinvention is to easily and cheaply provide in quantities tuning fork timepieces high in accuracy by using as a mechanical oscillator an addedy mass type circular tuning fork of which less oscillating energy leaks out and lthe quality factor Q is high.

Another object of the present invention is to provide small tuning fork timepieces high in accuracy by arranging -an electromagnetically driving device inside a circular cubicle surrounded by tines of the tuning fork high in quality factor Q so that the circular tuning fork may be excited by said electromagnetically driving device and a rotary disk may be rotated by the oscillating circular tuning fork.

An embodied watch of the present invention shall now be explained with reference to the accompanying drawings.

FIGURE l is an internal plan view of a circular tuning fork watch embodying the present invention, illustrating specically the arrangement of the driving part.

FIGURE 2 is a sectioned side view of the same, illustrating speciiically the rotary wheel train part.

FIGURE 3 is a magnified perspective view of the part of converting the oscillation of the circular tuning fork to a rotary motion and the part of adjusting means of the frequency of the circular tuning fork as taken out.

FIGURE 4 shows a wiring diagram of a driving circuit for the circular tuning fork.

FIGURE shows the relative positions of the magnetic poles of a permanent magnet carried by the tip of the tuning fork and magnetic pieces on a rotary disk to explain the principle of converting the oscillating motion to a rotary motion of the rotary disk by the attraction of the magnet attached to the tip of the circular tuning fork.

3,216,138 Patented Nov. 9, 1965 rice FIGURE `6 illustrates another embodiment of the rotary disk wherein each outer magnetic piece and each inner magnetic piece are connected with each other in one place to make the manufacture of the rotary disk easy.

FIGURE 7 illustrates a further embodiment wherein each outer magnetic piece and each inner magnetic piece are connected with each other in two places to further make the manufacture of the rotary disk easy.

lIn FIGURE l, 1 is a case of a watch, 2 is a circular tuning fork, 2' is an added mass secured to each tip of said circular tuning fork and 3 is a supporting part of said tuning fork. Said supporting part 3 is acute angle wedge-shaped at one end so as to be secured with an area as small as possible to the near of a nodal point in the center of the circular tuning fork and is secured at the other end, =for example, to the S pole side of a permanent magnet 4 for the element of the drivin-g device.

5 is an iron core of a driving coil. 5' is an iron core of a detecting coil. 6 is a driving coil wound on the above mentioned iron core 5. 6 is a detecting coil wound on the above mentioned iron core 5. 7 is an arcuate yoke arranged to be substantially concentric with the above mentioned circular tuning fork. Said yoke is secured in the center, for example, to the N pole side of the above mentioned permanent magnet 4 for the element of the driving device and is secured at the respective ends to the above mentioned iron cores 5 and 5 so as to form a closed magnetic circuit together with the center side of said circular tuning fork and the above mentioned supporting part 3. Said circular tuning fork 2, supporting part 3, yoke 7 and iron cores 5 and 5 are integrally itted to the case 1 by the magnet 4.

8 is a battery arranged substantially in the center of the case 1 inside the above mentioned yoke 7. Said battery 8 should be small in size and high in performance and may be, for example, a mercury battery.

9 is a transistor, 10 is a condenser and 11 is a resistor. Said transistor, condenser and resistor are contained in a space surrounded by the circular tuning fork 2 and battery 8. 12 is a rotary disk. 13 is an eccentric cam for adjusting the lfrequency of the tuning fork. 16 is a small permanent magnet secured to each tip of the above mentioned circular tuning fork. The above mentioned rotary disk 12 is rotatably fitted between the magnetic poles of said small permanent magnet. 14 is a hand setter. 15 is a starting knob. In starting of this watch, said knob 15 is operated so that the above mentioned rotary disk 12 may be rotated substantially at its synchronized speed through the gear mechanism. (The details of the opera tion shall be described later.) The rotation of the rotary disk 12 will be transmitted to a second hand 26, minute hand 27 and hour hand 28 through an inside mechanism 25 of a reduction gear mechanism 24 with a pinion 23 as illustrated in FIGURE 2. These mechanisms are arranged as thinly as possible in the upper part of the case 1.

16 is a small permanent magnet secured to each of the two tips of the circular tuning fork 2. 19 is a rotary disk body means made of a nonmagnetic material so as to be a base of the rotary disk 12. 17 is an outer magnetically high permeable magnetic piece fixed to said rotary disk body 19. 18 is an inner high permeable magnetic piece lixed to the same. The magnetic pieces may be formed by etching (as in printed Wiring) by pastin-g a magnetic sheet to each side of a thin rotary disk. However, in such case, the attraction of the magnet 16 for the magnetic pieces will somewhat reduce. 22 is a rotary shaft of the rotary disk 12. 23 is a pinion.

The oscillating action of the circular tuning fork 2 in the tuning fork timepiece according to the present invention shall be described in the following.

When the battery 8 is connected in the circuit shown in FIGURE 4, the tuning fork 2 will begin to oscillate due to the driving device consisting of the driving coil 6, transistor 9, detecting coil 6', condenser 10 and resistance 11. Each tine of the tuning for-k will oscillate to ri-ght and left, its amplitude will be the largest at the tip4 and the permanent magnet 16 at each tip will reciprocate very approximately linearly in the diametral direction on the rotary disk 12 because the amplitude at the tips is very small compared with length of the tines. (See FIGURE 5.) As the circular tuning fork is uniformly curved and has no part in which the internal strain is concentrated as in general tuning forks, the `quality factor Q will :be high and the frequency will be stable.

Now, the operation of the rotary disk 12 driven by the oscillating circular tuning fork 2 shall be described. In

FIGURE 5, the small hatched circles a, b and c represent.

the opposed positions on the rotary disk 12 of the magnetic poles of the permanent magnet 16 secured to the tip of the circular tuning fork 2. a is the position when the circular tuning fork 2 is stationary. b and c are the positions at the largest amplitude in case the circular tuning fork 2 oscillates.

Here, if the tuning fork 2`begins to oscillate as mentioned above and the magnetic poles have oscillated from b to c, in the positions in FIGURE 5, the rotary disk 12 will not rotate in any direction. Now, if the rotary disk 12 is rotated clockwise (in the direction indicated by the arow) with the starting knob 15, while the magnetic poles of the permanent magnet 16 reach the position c through the postion a from the position b, the magnetic poles will come somewhat closer to the inner magnetic piece 18 from the middle between the inner magnetic pieces 18 and 18 and therefore the inner magnetic piece 18 will be attracted stronger than piece 18 in the rotating direction by the attraction of the permanent magnet. Then, in case the magnetic poles oscillate to the other side from the position c to the position a through the position b, in the same maner, due to the inertia of the rotation of the rotary disk 12, the magnetic poles will come somewhat closer to the outer magnetic piece 17" from the middle between the outer magnetic pieces 17 and 17" and therefore the outer magnetic piece 17" will be attracted stronger in the rotating direction. Thus, the magnetic pieces will be attracted in turn and the rotary disk 12 will continue to rotate as synchronized with the frequency of the circular tuning fork 2.

In the above described embodiment, as mentioned above, the rotary disk 12 is made by inserting magnetic pieces to the rotary disk body 19 made of a nonmagnetic material. Such rotary disk has a defect that an ingenious technique is required to make it.

However, as another embodiment, there can be considered a rotary disk 12 wherein each outer magnetic piece 17 and each inner magnetic piece 18 are connected in one place 20 as illustrated in FIGURE 6 in order to make the manufacture of the rotary disk easy. In this embodiment, such thing as the rotary disk body 19 is unnecessary and the rotary disk is integrally formed of a disk made of a magnetic material and is therefore easy to make. However, the connecting part 20 should be wide enough to securely hold the outer magnetic piece 17.

As a further embodiment, there can be used a rotary disk 12 wherein each outer magnetic piece 17 and each inner magnetic piece 18 are connected in two places 21 and 22 as illustrated in FIGURE 7. In this embodiment, the outer magnetic piece can be more securely formed. In the same manner as in the above, the outer magnetic piece must be securely held by the connecting parts 21 and 22.

Further, as the cam 13 for adjusting the speed is an eccentric cam, by varying its rotating angle, the attraction between said cam and the magnet secured to the tuning fork by the leaking magnetic flux of the permanent magnet 16 can be varied so that the frequency of the circular tuning fork 2 may be regulated and rates of the watch may be adjusted.

As the present invention is formed as described above, the supporting part of the circular tuning fork is made common to the iitting part of the electromagnetic driving elements including the permanent magnet and can be therefore securely fixed. Therefore, the mechanical impedance of the supporting part will be larger, the leakage of the oscillating energy of the tuning fork will be smaller, the quality factor Q of the tuning fork will be higher and the accuracy of the watch will be improved. Further, as the tuning fork is circular and is supported on the inside nearer to the center of gravity of the tines, it will be more shockproof.

Further, according to the present invention, as the tuning fork is made circular so that all the parts of the driving device and the gears may be contained inside space surrounded by it, the space can be utilized most effectively and small flat tuning fork timepieces can be made. j

What is claimed is:

1. An electronic watch comprising the combination of a housing, a rotary indicating mechanism mounted within said housing, a supporting member mounted on said housing, a circular tuning fork comprising a split circular annulus made of a resilient material with the split forming a pair of outwardly curved tines adapted to vibrate alternately toward and away from each other at a predetermined natural frequency of vibration, said tuningfork being secured to said supporting member at a point diametrically opposed to said split with the outwardly curved tines of the tuning fork extending along the walls of the timepiece housing and around the rotary indicating mechanism, a battery mounted within the space between the outwardly curved tines of the tuning fork so as to form an annular chamber `between said battery and said circular tuning fork, an arcuate yoke disposed within said annular chamber adjacent to said battery and including a pair of magnetic cores extending radially toward the opposed tines of said tuning fork, said cores being symmetrically arranged with respect to said tines, a permanent magnet having one pole connected to said supporting member and the other pole connected to said yoke for magnetizing said cores, an electronic control circuit connected to said battery and mounted within said annular chamber for vibrating the tines of said tuning fork, said control circuit including a driving coil disposed around one of said magnetic `cores for applying periodic driving impulses to the tuning fork and a control coil disposed around the other of said magnetic cores for controlling the frequency of said driving impulses in response to the vibratory motion of the tuning fork, a pair of added masses one of which is mounted on one of said tines and the other of which is mounted on the other of said tines, said added masses and said tuning fork being adapted to provide a single nodal point in the vibratory motion of said fork, said nodal point being located at the point where said tuning fork is connected to said supporting member, and a rotary member operatively associated with the tines of said tuning fork for rotation in accordance with the vibration of said tines, said rotary member being coupled to the rotary indicating mechanism for driving the same.

2. In a timepiece including a rotary indicating mechanism mounted within a housing, the combination of a circular tuning fork comprising a split circular annulus made of a resilient material with the split forming a pair of curved tines adapted to vibrate alternately toward and away from each other at a predetermined natural frequency of vibration, said circular tuning fork being mounted within said housing with said curved tines eX- tending along the side walls of the housing and around the rotary indicating mechanism, a pair of added masses one of which is mounted on one of said tines and the other of which is mounted on the other of said tines, said masses being symmetrically located with respect to each other and with respect to said fork, said added masses and said tuning fork being adapted to provide a single nodal point in the vibratory motion of said tuning fork, supporting means mounted on said housing and secured to said tuning fork at said single nodal point, a transducer operatively associated with said tuning fork for vibrating the tines thereof and an electronic control circuit for energizing said transducer to sustain the vibratory motion of the tuning fork at a predetermined frequency, said transducer and said electronic control circuit being mounted on said housing in the space between the curved tines of said circular tuning fork, and a rotary member operatively associated with the tines of said tuning fork for rotation in accordance with the vibration of said tines, said rotary member being coupled to the rotary indicating mechanism for driving the same.

3. In a timepiece including a rotary indicating mechanism mounted within a housing, the combination of a circular tuning fork comprising a split circular annulus made of a resilient material with the split forming a pair of curved tines adapted to vibrate alternately toward and away from each other at a predetermined natural frequency of vibration, said circular tuning fork being mounted within said housing with said curved tines extending along the side walls of the housing, permanent magnets mounted on the ends of both tines of said tuning fork with the masses of said magnets and said tuning fork being adapted to provide a single nodal point in the vibratory motion of said tuning fork, supporting means mounted on said housing and secured to said tuning fork at said single nodal point, a battery mounted within the space between the outwardly curved tines of the circular tuning fork so as to form an annular chamber between said battery and said circular tuning fork, a transducer operatively associated with said battery and said tuning fork for vibrating the tines of said fork and an electronic control circuit for energizing said transducer to sustain the vibratory motion of the tuning fork at a predetermined frequency, said transducer and said electronic control circuit being mounted on said housing in said annular chamber between the battery and the tuning fork, and a rotary member magnetically coupled to the permanent magnets on the ends of said curved tines for rotation in accordance with the vibration of said tines, said rotary member being coupled to the rotary indicating mechanism for driving the same.

4. An electronic watch comprising the combination of a housing, a rotary indicating mechanism mounted within said housing, a circular tuning fork comprising a split circular annulus made of a resilient material with the split forming a pair of outwardly curved tines adapted to vibrate alternately toward and away from each other at a predetermined natural frequency of vibration, said circular tuning fork being mounted within said housing so as to form a circular cavity containing the rotary indicating mechanism, a pair of added masses one of which is mounted on one of said tines and the other of which is mounted on the other of said tines, said added masses and said tuning fork being adapted to provide a single nodal point in the vibratory motion of said tuning fork, a battery mounted within said circular cavity between the outwardly curved tines of the tuning fork so as to form an annular chamber between said battery and said tuning fork, supporting means mounted on said housing within said annular chamber and secured to said tuning fork at said single nodal point, a transducer mounted on said housing within said annular chamber, said transducer being operatively associated with said battery and said tuning fork for v-ibrating the curved tines at a predetermined frequency, an electronic control circuit mounted on said housing within said annular chamber, said control circuit being operatively associated with said battery and said transducer for sustaining the vibratory motion of the tuning fork at said predetermined frequency, and a rotary member mounted on said housing between the ends of said curved tines and magnetically associated with said added masses on said tines for rotation in accordance with the vibration of said tines, said rotary member being coupled to the rotary indicating mechanism for driving the same.

References Cited by the Examiner UNITED STATES PATENTS 2,571,085 10/51 Clifford 310-103 3,079,748 3/63 Hultqu'ist 58--23 FOREIGN PATENTS 1,281,667 12/61 France.

OTHER REFERENCES Electric Tuning Fork Beats Time for Accuracy, Machine Design, Oct. 27, 1960, pp. 30 and 31.

LEO SMILOW, Primary Examiner.

LEYLAND M. MARTIN, Examiner. 

1. AN ELECTRONIC WATCH COMPRISING THE COMBINATION OF A HOUSING, A ROTARY INDICATING MCHANISM MOUNTED WITHIN SAID HOUSING, A SUPPORTING MEMBER MOUNTED ON SAID HOUSING, A CIRCULAR TUNING FORK COMPRISING A SPLIT CIRCULAR ANNULUS MADE OF A RESILIENT MATERIAL WITH THE SPLIT FORMING A PAIR OF OUTWARDLY CURVED TINES ADAPTED TO VIBRATE ALTERNATELY TOWARD AND AWAY FROM EACH OTHER AT A PREDETERMINED NATURAL FREQUENCY OF VIBRATION, SAID TUNING FORK BEING SECURED TO SAID SUPPORTING MEMBER AT A POINT DIAMETRICALLY OPPOSED TO SAID SPLIT WITH THE OUTWARDLY CURVED TINES OF THE TUNING FORK EXTENDING ALONG THE WALLS OF THE TIMEPIECE HOUSING AND AROUND THE ROTARY INDICATING MECHANISM, A BATTERY MOUNTED WITHIN THE SPACE BETWEEN THE OUTWARDLY CURVED TINES OF THE TUNING FORK SO AS TO FORM AN ANNULAR CHAMBER BETWEEN SAID BATTERY AND SAID CIRCULAR TUNING FORK, AN ARCUATE YOKE DISPOSED WITHIN SAID ANNULAR CHAMBER ADJACENT TO SAID BATTERY AND INCLUDING A PAIR OF MAGNETIC CORES EXTENDING RADIALLY TOWARD THE OPPOSED TINES OF SAID TUNING FORK, SAID CORES BEING SYMMETRICALLY ARRANGED WITH RESPECT TO SAID TINES, A PERMANENT MAGNET HAVING ONE POLE CONNECTED TO SAID SUPPORTING MEMBER AND THE OTHER POLE CONNECTED TO SAID YOKE FOR MAGNETIZING SAID CORES, AN ELECTRONIC CONTROL CIRCUIT CONNECTED TO SAID BATTERY AND MOUNTED WITHIN SAID ANNULAR CHAMBER FOR VIBRATING THE TINES OF SAID TUNING FORK, SAID CONTROL CIRCUIT INCLUDING A DRIVING COIL DISPOSED AROUND ONE OF SAID MAGNETIC CORES FOR APPLYING PERIODIC DRIVING IMPULSES TO THE TUNING FORK AND APPLYING PERIODIC DISPOSED AROUND THE OTHER OF SAID MAGNETIC CORES FOR PERIODIC TROLLING THE FREQUENCY OF SAID DRIVING IMPULSES IN RESPONSE TO THE VIBRATORY MOTION OF THE TUNING FORK, A PAIR OF ADDED MASSES ONE OF WHICH IS MOUNTED ON THE OTHER TINES AND THE OTHER OF WHICH IS MOUNTED ON ONE OF SAID OF SAID TINES, SAID ADDED MASSES AND SAID TUNING FORK BEING ADAPTED TO PROVIDE A SINGLE NODAL POINT IN THE VIBRATORY MOTION OF SAID FORK, SAID NODAL POINT BEING LOCATED AT THE POINT WHERE SAID TUNING FORK IS CONNECTED TO SAID SUPPORTING MEMBER, AND A ROTARY MEMBER OPERATIVELY ASSOCIATED WITH THE TINES OF SAID TUNING FORK FOR ROTATION IN ACCORDANCE WITH THE VIBRATION OF SAID TINES, SAID ROTARY MEMBER BEING COUPLED TO THE ROTARY INDICATING MECHANISM FOR DRIVING THE SAME. 